This invention relates generally to electrical meters and the manufacturing process of electrical meters and more particularly to simplifying the current transformer assemblies, terminal strip, and connections typically used within electrical meters.
Electrical meters, such as revenue meters, are used by energy suppliers to accurately measure electrical energy delivered to customers for the purposes of billing and/or collecting revenue, and power quality meters having power quality monitoring, detection and reporting capabilities. There will typically be an electrical energy meter, such as a revenue meter, at a customer""s facility connected between the customer and the power distribution network to measure the customer""s electrical demand. The energy meter is an electrical energy measurement device, which accurately measures the amount of electrical energy flowing to the customer from the supplier or from the customer to the supplier. The amount of electrical energy measured by the meter is then used to determine the amount that the energy supplier should be compensated.
The deregulation of the electric utility industry has created a larger need for such electrical power measurement devices. Additionally, as technology advances and consumers become more reliant on electricity for their business needs, the need for devices that perform more complex functions and contain more features, and thus circuitry, is imposed upon the manufacturers. However, to keep up with the deregulation, many consumers are required to replace and install these new complex devices into existing cutouts or enclosures, and further these cutouts are often cut to pre-defined standard sizes. These standard enclosure or cutout sizes are often old as they have generally been in place for several years, if not several decades, thus the rapidly advancing technology has had to conform to the older standards. Accordingly, there is a need for more a compact device that still meets the requirements of the relevant physical and electrical standards.
As devices have become more compact, however, designers have often had to sacrifice mechanical reliability for space. For example, a designer may want to include supports in a device to ensure the delicate circuitry and associated connections are not damaged when the device is handled. However, with space restrictions the designer may be required to reduce these supports, or eliminate them entirely, thereby effectively decreasing the reliability of the device. Accordingly there is a need for a more compact device that still meets mechanical reliability needs.
Some known current transformers (xe2x80x9cCTsxe2x80x9d) are assembled separately in separate enclosures with a wire harness soldered by hand from the internal meter electronics to each of the transformer connections. Soldering the wire harnesses to the individual connections is time consuming since it introduces additional manufacturing steps. Alternately, CTs are also assembled separately using direct solder connections to the terminals in question. In both processes, providing the CT with a separate enclosure adds extra cost and time in the assembly process and introduces potential for errors and manufacturing defects.
Since the CT has secondary copper coil windings of typically 34-37 gauge (approximately xc3x80.005xe2x80x3), solder connections on such thin wire are susceptible to breakage if handled or jostled improperly. Thus, encasing the connections in resin increases the reliability of the circuitry and the entire power meter. Some devices, such as semiconductor chips, are encased in resin and have leads or wires extending out of the resin or enclosure. Some methods produce semiconductor parts by sealing the parts in a resin. However, these methods were intended for low cost solutions or low voltage devices and the electrical spacing and resin insulation were typically not considered. In known energy meters, the CTs are subject to potentially high voltage inputs thus are subject to various electrical specifications, described below.
In some devices, such as power meters, CTs are encased in resin in a separate enclosure. The enclosure is then assembled into the final product. CTs are required to be either physically spaced apart or electrically insulated due to the potentially high voltages connected to the device. Such an assembly can encase a transformer subassembly, except for the primary and secondary coil leads, in an epoxy resin, or encase a transformer with insulating material during an injection molding process. The extra steps of creating a subassembly can be time consuming and costly as an extra enclosure is required, plus the additional step of handling the transformer and enclosure is required during the final assembly process. The additional step of handling the transformer also may increase the chances of introducing manufacturing defects. Thus, there is a need for an improved device and assembly.
The invention is defined by the claims, and nothing in this section should be taken as a limitation on the claims.
As the complexity of devices grows, the size of the required circuitry often increases. However, in this age of rapidly advancing technology, consumers often expect the device to remain the same size or become physically smaller. In order to meet these needs or expectations a manufacturer reduces the size of a device while still adhering to the appropriate standards.
The present system and method can simplify and reduce the size of the assembled transformers installed within the enclosure of an intelligent electronic device. The enclosure houses electrical circuitry and a transformer that includes windings. A resin is set within the enclosure. The resin electrically isolates the windings of the transformer from analog circuitry. A central processing unit is housed within the enclosure. The central processing unit is coupled to the analog circuitry and operative to calculate at least one power management function. At least one of a display and a communications interface is housed within the enclosure and coupled to the central processing unit. Further aspects and advantages of the invention are discussed below in conjunction with the preferred embodiments.